How to implement discretionary use of Scanner

Question

I'm a Java newbie, so I apologize in advance if this is trivial. But, I have a simple calculator that prints the cost of 'a' items by 'b' dollars, but if you have more than 'c' items, then it costs 'd' dollars. The code for that is:

Scanner sc = new Scanner(System.in);
    int a = sc.nextInt(), b = sc.nextInt(), c = sc.nextInt(), d = sc.nextInt();

    if (a < b){
        System.out.printf("%d", a * c);
    }
    if (a == b){
        System.out.printf("%d", a * c);

    }
    if (a > b){
        System.out.printf("%d", a * d);
    }

but I'd like to add a bit more flexibility and avoid ambiguity, that is, the user inputs something like a=10 b=5 c=4 d=10 or b=5 d=10 a=10 c=4 (or any combination) all on one line, and the output is 100 for both. So, my question is how can I make it so that the order in which the user inputs the variables is arbitrary, all whilst keeping the same functionality?

TIA

Answer 1

You can do something like as follows:

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scannner = new Scanner(System.in);
        System.out.println("Enter the values: ");
        String input = scannner.nextLine();// Scan the complete line

        // Split the input on whitespace
        String[] parts = input.split("\\s+");

        // Create a Map with parts
        Map<String, Integer> map = new HashMap<>();
        for (String part : parts) {
            // Split on '='
            String[] tokens = part.split("=");
            map.put(tokens[0], Integer.valueOf(tokens[1]));
        }

        // The following processing is similar to what you are already doing
        if (map.get("a") < map.get("b")) {
            System.out.printf("%d", map.get("a") * map.get("c"));
        }
        if (map.get("a") == map.get("b")) {
            System.out.printf("%d", map.get("a") * map.get("c"));

        }
        if (map.get("a") > map.get("b")) {
            System.out.printf("%d", map.get("a") * map.get("d"));
        }
    }
}

A sample run:

Enter the values: 
a=10 b=5 c=4 d=10
100

Another sample run:

Enter the values: 
b=5 d=10 a=10 c=4
100

Note: This solution is to guide you progress. There is a lot to be done (e.g. validations, exception handling etc.) in order to make it better.

Answer 2

Try this:

import java.util.Scanner;

public class SimpleCalculatorScanner {
    public static void main(final String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] variables = sc.nextLine().split(" ");
        int a = 0;
        int b = 0;
        int c = 0;
        int d = 0;
        for(int i = 0; i < variables.length; i++) {
        try {
            if(variables[i].substring(0, 2).equals("a=")) {
                a=Integer.parseInt(variables[i].substring(2));
            }else if(variables[i].substring(0, 2).equals("b=")) {
                b=Integer.parseInt(variables[i].substring(2));
            }else if(variables[i].substring(0, 2).equals("c=")) {
                c=Integer.parseInt(variables[i].substring(2));
            }else if(variables[i].substring(0, 2).equals("d=")){
                d=Integer.parseInt(variables[i].substring(2));
            }else {
                System.out.println("Unrecognized variable "+variables[i].substring(0, 1)+" detected");
                return;
            }
        }catch(NumberFormatException e) {
            System.out.println("The character you assigned to variable "+variables[i].substring(0, 1)+" isn't a number");
            return;
        }           }
        if (a < b){
            System.out.printf("%d", a * c);
        }
        if (a == b){
            System.out.printf("%d", a * c);

        }
        if (a > b){
            System.out.printf("%d", a * d);
        }
    }
}

Sample I/O

Input

b=5 d=10 a=10 c=4

Output

100

Input 2

b=5 d=10 e=10 c=4

Output 2

Unrecognized variable e detected

Input 3

a=10 b=5 c=4 d=iforgot

Output 3

The character you assigned to variable d isn't a number

How it works

The Scanner reads a new line, and then turns it into an array by splitting every space.

Once the variables have been stored into an array, we run a for loop to test whether the first 2 characters of each item of the array are a=, b=, c= or d=. If it is a=, then it parses the every character after the = of the item in the array into an integer, and assigns it to variable a, vice versa.

If it doesn't recognize the variable, it will print Unrecognized variable <variablename> detected.

If the character assigned to the variable wasn't a number, it will print The character you assigned to variable <variablename> isn't a number